The invention relates to a vehicle, particularly a working machine, and a method for operating a vehicle. More particularly, the invention relates to a vehicle with improved operation safety.
It is known in the art that working machines such as excavators that are equipped with a pendulum axle and a pivotable boom can meet operating conditions where the inclination of the boom may introduce a risk of tilting over of the working machine. To reduce the risk of such unwanted behaviour of the working machine the operator usually locks the pendulum axle manually for instance by pressing a pushbutton in such working conditions. However, operating conditions may change rapidly when hauling load with the boom.
EP 1426207 A2 discloses an angular sensor arranged in a rotating electrical joint between the upper carriage and the undercarriage of an excavator. The electrical joint is arranged at a rotating thrust bearing device which enables a rotation of the upper carriage relative to the undercarriage. The electrical joint has a number of axially stacked and coaxially arranged disks as electrical contacts. Each disk is contacted with a brush forming a sliding electrical contact on the disk. One disk is an angular sensor defining an angular safety range in which the arm mounted at the upper carriage can be rotated about the horizontal axis without violating a stability criterion of the excavator and consisting of an electrically conductive section of the disk which is otherwise electrically insulating. The angular width of the electrically conductive section corresponds to the angular safety range. The pendulum axle of the excavator is automatically blocked when the rotation of the arm is beyond the angular safety range.
It is desirable to provide a vehicle, particularly a working machine, which has an improved operation comfort and safety for the operator. It is also desirable to provide a method for operating a vehicle in an improved manner regarding comfort and safety.
According to a first aspect of the invention, a vehicle is proposed, particularly a working machine, comprising at least one of (i) an undercarriage and an upper carriage arranged rotatably about a vertical axis with respect to the undercarriage and (ii) an undercarriage and an upper carriage a leverage means arranged pivotably about a horizontal axis with respect to the upper carriage, wherein a sensor system is provided for monitoring at least one stability criterion with respect of a tilt movement of the vehicle, and wherein a control unit is coupled to the sensor system for automatically initiating an action and/or performing an action for stabilizing the vehicle depending on the at least one stability criterion. The stability criterion can be a desired weight distribution which provides a stable position of the vehicle. The weight distribution of the vehicle can be varied e.g. by rotating the upper carriage with respect to the undercarriage and/or by changing the inclination of the leverage means.
The sensor system comprises a sensor unit for monitoring the position of the upper carriage with respect to the undercarriage. The sensor system is provided for monitoring a position of the upper carriage with respect to the undercarriage and an inclination and/or length of the leverage means with respect to the upper carriage. By selecting such elements which may contribute alone or in combination to an instable position of the vehicle for monitoring and reacting appropriately, safe operation of the vehicle can be increased. The operator can concentrate on operating the vehicle and the tools attached to the vehicle.
One or more detecting plates can be arranged at a circumferential portion of a turntable between the upper carriage and the undercarriage being in operative connection with at least one detector for detecting a movement of the one or more detecting plates relative to the detector. For instance, the sensor can issue a signal if and as long as the rotational position of the upper carriage with respect to the undercarriage is in a tolerable range which is stable independent of the inclination of the boom and/or arm and otherwise not. Alternatively, the sensor can issue a signal if and as long as the position of the upper carriage with respect to the undercarriage is in a range which may generate an instable condition dependent of the inclination of the boom and/or arm and otherwise not In other words the sensor (comprising one or more detecting plates and one or more detectors) will issue a signal if and as long as the detecting plate is in an operative connection with the detector and irrespective whether or not the vehicle is in an unstable condition. The control unit that receives the sensor signals will evaluate them and further input signals and will issue a signal if an unstable condition for the vehicle is detected.
The leverage means can be a boom or the like. Depending on the inclination and/or length of the leverage means, weight of the leverage means (and, where applicable, including its load) can add to another weight at a particular location of the vehicle which under unfavourable overall weight distribution conditions can overload a certain part of the vehicle which in turn can have the effect that the vehicle tilts over. The vehicle can for instance be a working machine as an excavator with a tiltable leverage means, a pipe layer with a fixed arm, a material handler for handling goods e.g. in a harbour, a demolition machine for demolition of e.g. buildings, an excavator with a telescope arm, and the like.
Generally, the vehicle can be positioned on even ground or on a slope. Therefore, it is advantageous in a preferred embodiment of the invention to provide the vehicle also with an inclination sensor which indicates the inclination of the vehicle relative to the horizontal plane so that the information about the sensed position and/or inclination of the upper carriage and/or the leverage means can be combined together with the sensed inclination of the vehicle on the slope relative to the horizontal plane as input parameters for the control unit according to the invention.
The slope on which the vehicle is positioned can either improve the stability of the vehicle or increase the risk of instability, depending on how the undercarriage and the upper carriage are positioned with respect to the slope. For instance, with a vehicle on a slope the rotational position of the upper carriage alone (i.e. in cases where the influence of any leverage means of the vehicle on the stability of the vehicle is negligible) with respect to the undercarriage as well as with respect to the inclined ground can cause instability of the vehicle. If the vehicle is on a slope, in the preferred embodiment of the invention the control unit can send a warning signal to the vehicle's operator when a risk of instability is detected which, on even ground, would not induce any instability risk, or, alternatively or in addition, the control unit can automatically initiate an action and/or perform an action for stabilizing the vehicle in such a situation. In doing so the risk that this unwanted instability of the vehicle occurs can be considerably reduced even in cases where the operator had not manually initiated a stabilization of the vehicle before starting the working operation when the vehicle is on a slope. As a further advantage it is noted that an operator of such a vehicle is less distracted from the operation of the vehicle under working conditions because he is being released (i) from being forced to interrupt the work he is carrying out in order to manually initiate the stabilization of the vehicle, e.g. by locking or braking a pendulum axle or the like, or (ii) from continuously watching the necessity to initiate such stabilization.
A pendulum axle has wheels of the vehicle (for instance of an excavator) (i) directly attached to axle portions of the pendulum axle or (ii) pivotably attached in case the pendulum axle is a steerable axle of the vehicle, resulting in a change of the wheel camber when cushioning or rebounding. These axle portions are pivotable with respect to a middle portion (e.g. a differential) of the pendulum axle.
When one of the wheels attached to the pendulum axle runs over an obstacle, the respective axle portion pivots with respect to the other axle portion, e.g. the wheel that hit the obstacle moves upward in order to roll over the obstacle. When the pendulum axle is locked, however, the axle portions cannot move or bend with respect to each other.
According to a favourable embodiment of the invention, the leverage means can comprise a boom pivotably attached to the upper carriage and usually also an arm pivotably attached to the boom. Particularly, the boom can be a monoboom with a pivot joint to the upper carriage and a pivot joint to the arm. The monoboom can be straight or bent. Alternatively, the boom can be a 2-piece boom where in between the two pivot joints mentioned above an additional pivot joint is arranged so that the boom consists of two portions which can be pivoted about a pivot axle, thus yielding a higher flexibility of the boom operation. It is possible to mount a sensor between the two boom parts in order to detect the relative positions of the two boom parts. In cases when the boom is in an upright position, e.g. in a most rearward position, and the upper carriage turns crosswise relative to the undercarriage, a heavy counterweight at the rear end of the upper carriage can cause a tilting over the rear end of the vehicle as the weight of the boom and arm add to the weight of the counterweight or, at least, does not compensate enough the weight of the counterweight. Particularly in cases where the vehicle is equipped with a pendulum axle, this can result in an instable position as the side of the pendulum axle which experiences this load can give way and the vehicle can tilt.
According to a favourable embodiment of the invention, a pendulum axle of the undercarriage can be automatically lockable and/or automatically brakeable depending on the at least one stability criterion. Particularly, the pendulum axle can be a front axle of the vehicle which can also be a steering axle of the vehicle.
The pendulum axle can also be a rear axle. By automatically locking and/or automatically braking the pendulum axle the operator is released from monitoring the position of the upper carriage with respect to the undercarriage and the position of the boom. Even if the operator would forget to lock or to brake the pendulum axle manually, the pendulum axle will be secured as this is done automatically. Optionally, an additional warning can be issued to the operator.
If the locking or braking of the pendulum axle is not enough to reach a stable condition, one expedient measure is to stop the movement and/or to motivate the operator to rotate the leverage means and/or the upper carriage in that direction that is needed to stabilize the vehicle. Particularly, if the vehicle is located on a slope the operator can be motivated to change the location and/or position of the vehicle towards a position that is stable when conducting the planned operation.
According to a favourable embodiment of the invention, a detecting plate can be provided for monitoring the inclination and/or length of the boom with respect to the upper carriage. Expediently a sensor can be arranged in one or more pivotable joints of the leverage means, e.g. between the boom and an arm, so that the length of the leverage means can be derived from the relative pivot angels of pivotable sections of the leverage means.
For instance, the sensor can issue a signal if and as long as the inclination of the boom and/or arm sensor in pivotable joint between boom and arm is in a tolerable range independent of the rotational orientation of the upper carriage with respect to the undercarriage and otherwise not. Alternatively, the sensor can issue a signal if and as long as the inclination of the boom and/or arm is in a range which may be generate an instable condition dependent of the rotational orientation of the upper carriage with respect to the undercarriage and otherwise not In other words the sensor (comprising one or more detecting plates and one or more detectors) will issue a signal if and as long as the detecting plate is in an operative connection with the detector and irrespective whether or not the vehicle is in an unstable condition. The control unit that receives the sensor signals will evaluate them and further input signals and will issue a signal if an unstable condition for the vehicle is detected.
Generally all kinds of sensor units can be used, e.g. magnetic, optical, infrared sensor units and the like.
Favourably, the vehicle can be embodied as an excavator, for instance with a tillable leverage means or with a telescope arm. Favourably, the excavator provides a comfortable and safe operation. However, the vehicle can also be a pipelayer (for instance with a fixed arm), a material handler for handling goods e.g. in a harbour, a demolition machine for demolition of e.g. buildings, and the like.
According to another aspect of the invention, a method for operating a vehicle is proposed, particularly a working machine, wherein an upper carriage performs a rotational movement about a vertical axis with respect to an undercarriage comprising the steps of monitoring at least one stability criterion with respect of a tilt movement of the vehicle, and initiating automatically an action and/or performing an action for stabilizing the vehicle depending on the at least one stability criterion. The stability criterion can be a desired weight distribution which provides a stable position of the vehicle. By automatically initiating and/or performing an action for stabilizing the operator is released from additional work and can concentrate on operating the vehicle.
One or more detecting plates being arranged at a circumferential portion of a slew unit between the upper carriage and the undercarriage are in operative connection with at least one detector for detecting a movement of the one or more detecting plates relative to the detector, wherein                either the sensor issues a signal if and as long as the rotational position of the upper carriage with respect to the undercarriage is in a tolerable range which is stable independent of the inclination of a boom and/or arm and otherwise not; or the sensor issues a signal if and as long as the rotational position of the upper carriage with respect to the undercarriage is in a range which may generate an instable condition dependent on the inclination of a boom and/or arm and otherwise not; and        wherein the control unit receiving the sensor signals evaluates the sensor signals and further input signals and issues a signal if an unstable condition for the vehicle is detected.        
The vehicle can for instance be a working machine as an excavator with a tiltable leverage means, a pipe layer with a fixed arm, a material handler for handling goods e.g. in a harbour, a demolition machine for demolition of e.g. buildings, an excavator with a telescope arm, and the like.
According to a favourable method step, automatically locking and/or automatically braking a pendulum axle of the undercarriage is performed depending on the at least one stability criterion. Expediently, when a weight distribution of the vehicle is unfavourably and may cause instability of the vehicle during operation, the pendulum axle can be locked or braked automatically without interference of the operator.
According to a favourable method step, the steps can be provided of monitoring a position of the upper carriage with respect to the undercarriage; monitoring an inclination and/or a length of a leverage means (for instance a boom or a boom and an arm pivotably connected with the boom) with respect to the upper carriage; combining the monitored position and inclination and/or length for determining a risk of instability of the vehicle; comparing the combined monitored position and inclination and/or length with at least one stability criterion; and locking and/or braking a pendulum axle automatically as long as the at least one stability criterion is violated.
According to a favourable method step, locking and/or braking a pendulum axle can be performed automatically when neither a signal from a sensor monitoring a position of the upper carriage with respect to the undercarriage nor a signal from monitoring an inclination and/or a length of a leverage means (for instance a boom or a boom and an arm pivotably connected with the boom) with respect to the upper carriage is sent to a control unit for automatically initiating an action and/or performing an action for stabilizing the vehicle. Advantageously, locking or braking the pendulum axle is done only in cases where the weight distribution in the vehicle is critical so that risk of tilting of the vehicle is probable, i.e. exceeding a predefined threshold of probability. In other operational conditions the pendulum axle is unlocked and can provide its desired driving characteristics.
The method can be implemented as hardware, as software or as combination of hardware and software. Particularly, a computer program can be provided comprising a computer program code adapted to perform the inventive method or for use in a method when said program is run on a programmable microcomputer. The computer program can be adapted to be downloaded to a control unit or one of its components when run on a computer which is connected to the internet.
A computer program product stored on a computer readable medium can be provided, comprising a program code for use in the inventive method on a computer.